Voltage-dependent calcium channels (VDCC) are a group of voltage-gated ion channels found in excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the ion Ca2+. At physiologic or resting membrane potential, VDCCs are normally closed. They are activated (i.e., opened) at depolarized membrane potentials. Activation of particular VDCCs allows Ca2+ entry into the cell, which depending on the cell type, results in muscular contraction, excitation of neurons, up-regulation of gene expression, or release of hormones or neurotransmitters.
Voltage-dependent calcium channels are formed as a complex of several different subunits: α1, α2δ, and β1-4, and γ. The α1 subunit forms the ion conducting pore while the associated subunits have several functions including modulation of gating
The α2δ gene forms two subunits α2 and δ (which are both the product of the same gene). They are linked to each other via a disulfide bond and have a combined molecular weight of 170 kDa. The α2 is the extracellular glycosylated subunit that interacts with the α1 subunit. The δ subunit has a single transmembrane region with a short intracellular portion, which serves to anchor the protein in the plasma membrane.
Co-expression of the α2δ enhances the level of expression of the α1 subunit and causes an increase in current amplitude, faster activation and inactivation kinetics and a hyperpolarizing shift in the voltage dependence of inactivation. Some of these effects are observed in the absence of the beta subunit, whereas, in other cases, the co-expression of beta is required.
The α2δ-1 and α2δ-2 subunits are the binding site for at least two anticonvulsant drugs, gabapentin and pregabalin, that also find use in treating chronic neuropathic pain associated with diabetes, fibromyalgia, and shingles, as well as for the treatment of epilepsy and seizures. However, these drugs suffer from several adverse or side effects. These include dizziness, drowsiness, and peripheral edema. Also, children were observed to be susceptible to mild-to-moderate mood swings, hostility, concentration problems, and hyperactivity. Although rare, there are several cases of hepatotoxicity reported.
Therefore, pharmacotherapy with such therapeutic amino acids would be improved if these and/or other adverse or side effects associated with their use could be decreased or if their pharmacology may be improved. Thus, there is a large unmet need for developing novel amino acid compounds.
The present invention seeks to address these and other needs in the art.